; Flash LEDs on R/C Airplane.
; Initial goal: flash by taking output pin high for 100 ms every 500 ms. 
; This program expectes to run on an ATTINY12 with the 1.2 Mhz internal RC clock. 

   

;	T12astrobe081028A	Released version.
;	T12astrobe081027A	Initial code.


;	ASSIGNMENT OF PORTB I/O PINS
;0	500 ms interval, 100 ms on
;1	500 ms interval, 50 ms on
;2	250 ms interval, 100 ms on
;3	250 ms interval, 50 ms on
;4	10 Hz square wave
;5	Reset pin.
;6	Does not exist on AATTINY12.
;7	Does not exist on AATTINY12.

        
.include "tn12def.inc"

.equ	reload		= $CC					; Timer preload/reload value. $CC.
.def    temp    	= r16					; Scratch. 
.def	sregtemp 	= r17					; Place to save status register during interrupts.
.def	tempi 		= r18					; Scratch register for use in timer overflow register.
   
.ORG $0000      
        rjmp    reset
        reti                            ; External interrupt handler - not used.
        reti                            ; Pin change interrupt -not used.
        rjmp    tovflo                  ; timer overflow interrupt handler.
   
reset:  
     
   
        ldi     temp,0b00011111			; Load data direction value for PORTB.
        out     DDRB,temp               
        ldi     temp,0b00000000			; Start with all outputs low.
        out     PORTB,temp              
        ldi     temp,$80
        out     ACSR,temp               ; Turn off comparitor (save a little power)..
        ldi     temp,0b00000101
        out     TCCR0,temp              ; Set timer prescaler to clock/1024
   
        ldi     temp,reload				; Preload timer counter.
        out     TCNT0,temp
        ldi     temp,$02                ; Enable timer overflow interrupts.
        out     TIMSK,temp            

        sei                             ; Enable interrupts in general
        rjmp    main
   
   
;///////////////TIMER OVERFLOW SERVICE//////////////////         
tovflo:         
   
        in      sregtemp,SREG           ; Save the status register contents       
        ldi     tempi,reload			; Re-preload load counter. 
        out     TCNT0,tempi
        out     SREG,sregtemp           ; Restore the status register contents
        reti
 
 wait_50ms:					
   	ldi	temp,$22		;enable sleep and set T0 to respond to falling edge
	out	MCUCR,temp		;enable sleep mode
	ldi	temp,$40		;enable external interrupt 0	
	out	GIMSK,temp   
	sei				;assure interrupts are enabled
   	sleep  
	ret

.db	"Copyrights reserved Dick Cappels www.projects.cappels.org October 28, 2008 Code: T12astrobe081028A"

main:
	sbi		PORTB,0
	sbi		PORTB,1
	sbi		PORTB,2
	sbi		PORTB,3
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,1
	cbi		PORTB,3
	cbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,0
	cbi		PORTB,1
	cbi		PORTB,2
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,4
	rcall	wait_50ms
	sbi		PORTB,4
	rcall	wait_50ms
	sbi		PORTB,3
	sbi		PORTB,0
	sbi		PORTB,2
	cbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,3
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,0
	cbi		PORTB,2
	cbi		PORTB,4
	rcall	wait_50ms
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,4
	rcall	wait_50ms
;rjmp	main


	sbi		PORTB,0
	sbi		PORTB,1
	sbi		PORTB,4
	sbi		PORTB,2
	sbi		PORTB,3
	rcall	wait_50ms
	cbi		PORTB,1
	cbi		PORTB,3
	cbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,0
	cbi		PORTB,1
	cbi		PORTB,2
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,4
	rcall	wait_50ms
	sbi		PORTB,4
	rcall	wait_50ms
	sbi		PORTB,0
	cbi		PORTB,4
	sbi		PORTB,2
	sbi		PORTB,3
	rcall	wait_50ms
	cbi		PORTB,3
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,0
	cbi		PORTB,2
	cbi		PORTB,4
	rcall	wait_50ms
	sbi		PORTB,4
	rcall	wait_50ms
	cbi		PORTB,4
	rcall	wait_50ms	
	 
rjmp	main
 
;end of assembly souce listing